Added typings for gulp-terser (#35904)

Not much going on here since it imports all options from terser. Based
it losely on the pre-existing gulp-uglify and
webpack-terser-plugin typings as reference points

Signed-off-by: Jeroen Claassens <support@favware.tech>

types/gulp-terser/gulp-terser-tests.ts

@@ -0,0 +1,28 @@
+import * as gulp from 'gulp';
+import terser = require('gulp-terser');
+import pump = require('pump');
+
+gulp.task('basic terser', () => {
+    const tsResult = gulp.src('lib/*.ts')
+        .pipe(terser())
+        .pipe(gulp.dest('dist'));
+});
+
+gulp.task('terser with options', () => {
+    const tsResult = gulp.src('lib/*.ts')
+        .pipe(terser({
+            mangle: false,
+            compress: false,
+        }))
+        .pipe(gulp.dest('dist'));
+});
+
+gulp.task('terser with pump', (cb) => {
+    pump([
+            gulp.src('lib/*.js'),
+            terser(),
+            gulp.dest('dist')
+        ],
+        cb
+    );
+});

types/gulp-terser/index.d.ts

@@ -0,0 +1,13 @@
+// Type definitions for gulp-terser 1.2
+// Project: https://github.com/duan602728596/gulp-terser#readme
+// Definitions by: Jeroen "Favna" Claassens <https://github.com/favna>
+// Definitions: https://github.com/DefinitelyTyped/DefinitelyTyped
+// TypeScript Version: 3.0
+
+/// <reference types="node"/>
+
+import { MinifyOptions } from 'terser';
+
+export = terser;
+
+declare function terser(options?: MinifyOptions): NodeJS.ReadWriteStream;

types/gulp-terser/package.json

@@ -0,0 +1,7 @@
+{
+    "private": true,
+    "dependencies": {
+      "terser": "^4.0.0"
+    }
+  }
+  

types/gulp-terser/tsconfig.json

@@ -0,0 +1,23 @@
+{
+    "compilerOptions": {
+        "module": "commonjs",
+        "lib": [
+            "es6"
+        ],
+        "noImplicitAny": true,
+        "noImplicitThis": true,
+        "strictNullChecks": true,
+        "baseUrl": "../",
+        "typeRoots": [
+            "../"
+        ],
+        "types": [],
+        "noEmit": true,
+        "forceConsistentCasingInFileNames": true,
+        "strictFunctionTypes": true
+    },
+    "files": [
+        "index.d.ts",
+        "gulp-terser-tests.ts"
+    ]
+}

types/gulp-terser/tslint.json

@@ -0,0 +1 @@
+{ "extends": "dtslint/dt.json" }